1. Field of the Invention
The present invention relates to an endoscope.
2. Description of the Background Art
Endoscopic examination techniques have prevailed in a multiplicity of medical and veterinary fields of application. Here, an endoscope, which has an elongate shaft with an imaging optical system, is introduced into the interior of the body, for example into a cavity in the interior of the body, in order to record an image of an object field there and to transmit said image to outside of the body and thereby make it available for observation or evaluation. Increasingly, use is made of video endoscopes which have an electronic image recorder for recording the image of the object field.
In many cases, an examination of the tissue is essential for a reliable diagnosis. Contact endoscopes are known for this purpose; they have an optical system designed for contact with tissue to be examined in order to enable high-resolution imaging. In order to illuminate the object field, the illumination light generated by a light source arranged in the proximal region of the endoscope is usually guided with the aid of optical fibers to the distal end of the shaft of the endoscope, where it emerges distally, substantially in the axial direction. As a result of the small distance from the object field, a sufficiently bright and/or sufficiently homogeneous illumination of the object field often cannot be achieved in the case of contact endoscopes. For example, this applies to fluorescence examinations, wherein fluorescence excitation radiation is radiated in a short-wavelength wavelength range onto a tissue region to be examined and the fluorescence radiation emitted by the tissue is observed in a longer-wavelength wavelength range. At the same time, the admissible external diameter of the endoscope is very restricted in many applications, and so a miniaturized embodiment of the imaging optical system and of the illumination system is required.
DE 10 2006 046 555 B4, which corresponds to U.S. Pat. No. 7,511,891, which is incorporated herein by reference, describes a miniaturized optically imaging system with a high lateral and axial resolution, which is designed for endoscopic applications for example. The miniaturized optically imaging system comprises a refractive planoconvex homogeneous optical lens which, with the plane side thereof, defines a plane entry surface of the optical system, a first GRIN (Gradient-Index) lens for reducing the divergence of the light beam transmitted from the object field through the refractive lens and a second GRIN lens for adapting the light beam transmitted by the first GRIN lens to a subsequent optical transmission system to a sensor unit. Compared to the transmission length, the transmission system has a small diameter and it is embodied as e.g. a flexible image-guiding fiber bundle or as rigid relay optics. For the purposes of coupling light, a thin excitation fiber is arranged along the optical axis. For the purposes of fluorescence observations, a deflection element embodied as a beam splitter can be arranged between the first and the second GRIN lens, wherein the beam splitter has a dichroic beam-splitting coating, which passes the excitation light in transmission and deflects the radiation emitted by the object in a reflecting manner.
EP 1 545 290 B1, which corresponds to U.S. Pat. No. 7,662,095, which is incorporated herein by reference, discloses an endoscope for illuminating and observing object fields in cavities, which has an illumination unit and an image transmission system, assigned to which there is an objective on the distal side and eyepiece or camera optics as an observation system on the proximal side. An optical splitter element for mutually complementary light polarizations or wavelength regions and light polarizations is inserted on the proximal side between the illumination unit, the image transmission system and the observation system in such a way that the illumination light generated by the illumination unit can be coupled into the image transmission system.